1. Field of the Invention
The invention relates to heavy-duty vehicles and in particular to axle/suspension systems of heavy-duty vehicles such as semi-trailers. More particularly, the present invention is directed to a mount for the shock absorber component of axle/suspension systems. More specifically, the present invention relates to a shock absorber lower mount support assembly and method for installation, which includes placement of a support assembly on the inboard side of the shock mount assembly and wherein the support assembly is also mounted on the beam of its respective suspension assembly. This mounting arrangement and method of installation results in satisfactory conservation of the clamp load of the shock mount assembly at the shock absorber-shock mount interface, which in turn strengthens the connection of each shock absorber to its respective suspension assembly of the axle/suspension system, resulting in greater absorption of stresses, forces and/or loads encountered by the vehicle as it travels over the road, thereby minimizing the possibility of damage to the suspension assembly, hanger and/or vehicle frame.
2. Background Art
The use of air-ride trailing and leading arm rigid beam-type axle/suspension systems has been popular in the heavy-duty truck and tractor-trailer industry for many years. Although such axle/suspension systems can be found in widely varying structural forms, in general their structure is similar in that each system typically includes a pair of suspension assemblies. In some heavy-duty vehicles, the suspension assemblies are connected directly to the primary frame of the vehicle. In other heavy-duty vehicles, the primary frame of the vehicle supports a subframe, and the suspension assemblies connect directly to the subframe. For those heavy-duty vehicles that support a subframe, the subframe can be non-movable or movable, the latter being commonly referred to as a slider box, slider subframe, slider undercarriage, or secondary slider frame. For the purpose of convenience and clarity, reference herein will be made to main members, with the understanding that such reference is by way of example, and that the present invention applies to heavy-duty vehicle axle/suspension systems suspended from main members of: primary frames, movable subframes and non-movable subframes.
Specifically, each suspension assembly of an axle/suspension system includes a longitudinally extending elongated beam. Each beam typically is located adjacent to and below a respective one of a pair of spaced-apart longitudinally extending main members and one or more cross members that form the frame of the vehicle. More specifically, each beam is pivotally connected at one of its ends to a hanger, which in turn is attached to and depends from a respective one of the main members of the vehicle. An axle extends transversely between and typically is connected by some means to the beams of the pair of suspension assemblies at a selected location from about the mid-point of each beam to the end of the beam opposite from its pivotal connection end. The opposite end of each beam also is connected to an air spring, or its equivalent, which in turn is connected to a respective one of the main members. A height control valve is mounted on the hanger or other support structure and is operatively connected to the beam and to the air spring in order to maintain the ride height of the vehicle. A brake system and one or more shock absorbers, which provide damping to the vehicle axle/suspension system, are also included. The beam may extend rearward or frontward from the pivotal connection relative to the front of the vehicle, thus defining what are typically referred to as trailing arm or leading arm axle/suspension systems, respectively. However, for purposes of the description contained herein, it is understood that the term “trailing arm” will encompass beams that extend either rearward or frontward with respect to the front end of the vehicle.
The one or more axle/suspension systems of the heavy-duty vehicle act to cushion the ride, dampen vibrations and stabilize the vehicle. More particularly, as the vehicle is traveling over the road, its wheels encounter road conditions that impart various forces, loads, and/or stresses, collectively referred to herein as forces, to the respective axle on which the wheels are mounted, and in turn, to the suspension assemblies that are connected to and support the axle. In order to minimize the detrimental affect of these forces on the vehicle as it is operating, the axle/suspension system is designed to react and/or absorb at least some of these forces.
These forces include vertical forces caused by vertical movement of the wheels as they encounter certain road conditions, fore-aft forces caused by acceleration and deceleration of the vehicle, and side-load and torsional forces associated with transverse vehicle movement, such as turning of the vehicle and lane-change maneuvers. In order to address such disparate forces, axle/suspension systems have differing structural requirements. More particularly, it is desirable for an axle/suspension system to be fairly stiff in order to minimize the amount of sway experienced by the vehicle and thus provide what is known in the art as roll stability. However, it is also desirable for an axle/suspension system to be relatively flexible to assist in cushioning the vehicle from vertical impacts, and to provide compliance so that the components of the axle/suspension system resist failure, thereby increasing durability of the axle/suspension system. It is also desirable to dampen the vibrations or oscillations that result from such forces. A key component of the axle/suspension system that cushions the ride of the vehicle from vertical impacts is one or more air springs, while one or more shock absorbers typically provide damping characteristics to the axle/suspension system.
More particularly, shock absorbers have been used for many years on various types of prior art air-ride axle/suspension systems to dampen the vertical movement of the vehicle as it travels over the road. A typical prior art shock absorber is attached at its upper end to a shock upper mount assembly, which includes a clevis and fastener mounted on the hanger of its respective suspension assembly. The lower end of the shock absorber is mounted to the beam of its respective suspension assembly by a shock lower mount assembly. Thus, the shock absorber dampens vertical movement of the beam of its respective suspension assembly during operation of the vehicle.
The heavy-duty vehicle industry has progressively developed more robust shock absorbers with increased damping characteristics that provide greater control over a vehicle's vertical movement. However, the use of these more robust shock absorbers with increased damping characteristics can also require more robust mounting of the shock absorber. More specifically, when utilizing a more robust shock absorber with increased damping characteristics, the shock lower mount assembly can potentially exhibit a reduced clamp load and decreased durability over the life of the shock lower mount assembly when utilizing known means for mounting the shock lower mount assembly to its respective suspension beam. More particularly, when the clamp load of the shock lower mount assembly is compromised, the bolt of the shock lower mount assembly can loosen or bend, thereby decreasing shock lower mount assembly performance as well as potentially decreasing the life of the shock lower mount assembly. This potential reduced clamp load and decreased durability of the shock lower mount assembly can in turn result in increased maintenance and/or replacement costs and could potentially cause damage to the suspension assembly, shock absorber, hanger, or the vehicle frame, which could result in additional maintenance and or replacement costs.
The shock mount support assembly for heavy-duty vehicle axle/suspension systems of the present invention solves the above-noted problems by providing an improved shock lower mount support assembly and method for installation of the assembly that facilitates reduced stress at the shock lower mount interface to the beam of its respective suspension assembly. This is achieved due to the structure of the shock lower mount support assembly conserving the clamp load at the shock lower mount-beam interface, by providing a broader area of support to the shock lower mount-beam attachment interface, and by distributing loads from both the inboard and outboard attachment points of the shock absorber to the beam of its respective suspension assembly. By utilizing the shock mount support assembly for heavy-duty vehicle axle/suspension systems of the present invention, a more robust shock absorber can in turn be utilized on the vehicle to absorb forces common to highway travel with much greater efficiency and less risk of decreasing durability of the shock absorber, mounting structure and/or other components such as the vehicle frame, hanger or suspension assembly.